1. Field of the Invention
The invention relates to the field of snowmobiles. More particularly, the invention relates to skis for snowmobiles or other ski-mounted vehicles, with selectively deployable wheel units.
2. Description of the Prior Art
Snowmobiles are vehicles that are constructed to travel across snow and ice. As is generally known, the snowmobile is driven by an endless drive track arranged at the rear end of the underside of the snowmobile. The front end of the snowmobile is supported on two skis, which glide across the surface of the snow or ice. The skis typically have a carbide runner that runs along a portion of the bottom surfaces, to help keep the snowmobile traveling along a smooth track.
A disadvantage of snowmobiles is that the skis don't readily glide across gravel, hardtop, or other non-snow surfaces. This makes it difficult, if not impossible, to maneuver a snowmobile across a roadway, driveway, onto ferry, etc., because the skis do not respond properly to the steering operations initiated at the handlebars. Quite often, the snowmobile needs to be dragged or pushed on driveways and across roadways, etc. Furthermore, driving or dragging a snowmobile across a non-snow surface causes excessive wear on the carbide runners, which then have to be replaced.
In recent years, the sport of snowmobiling has evolved from one of traveling relatively short distances over trails close to home to one of weekend-long or longer cross-country trips. Previously, for example, a snowmobile operator would fill the gasoline tank of the snowmobile in his or her backyard, transport the snowmobile to a trail site or depart directly from the backyard for an afternoon or day of travel over snowmobile club trails, and then return home. Nowadays, people are traveling great distances across country on snowmobiles that involve two- or three-day tours or even such mammoth tours as from Alaska to Maine. Thus, where in the past the tank on the snowmobile was filled at home or at the point of departure before a daylong excursion, snowmobiles now need to be refilled while out traveling. This means that the snowmobile must be driven to a service station, typically by traveling some distance along a surface other than snow or ice, for example, along a asphalt road or gravel road. Also, it is not guaranteed for such lengthy trips that snow will always be available as a travel surface and, consequently, snowmobiles more and more frequently need to travel some distance across asphalt or gravel surfaces. When a snowmobile needs to be dragged or pushed only a short distance across a roadway or driveway, or up a ramp onto a ferry or trailer, it is possible for a person to do it alone or with the assistance of a traveling companion. Now, however, with the need to travel several miles along a roadway to get to a filling station, the inability to steer a snowmobile has become a major obstacle in the logistics and the enjoyment of the sport.
Efforts to make snowmobiles mobile on gravel or other surfaces have been undertaken over the years. Prior art includes conversion kits to replace the skis with wheels. These conversion kits were intended to replace the skis on a semi-permanent basis, that is, to convert a snowmobile into a wheeled vehicle for an extended period of time. Such conversion kits typically require that the ski be removed in order to mount the wheels, or, if the ski does remain attached to the vehicle, a longer kingpin must be used to mount the wheels. Thus, each time the wheels are mounted or removed, the kingpin must be replaced with the longer or shorter one, respectively. Both methods of converting the snowmobile to a wheeled vehicle involve a fair amount of work. Thus, such conversion kits are not generally an acceptable solution to the problem of having to change in relatively quick succession back and forth between a vehicle that rides on skis and one that rides on wheels, as happens when traveling over gravel or hardtop to fill the gas tank or to load onto a ferry or trailer.
The inventor of the present invention is also the inventor of several patents for wheel units for snowmobiles, all of which are incorporated herein in their entirety by reference: U.S. Pat. No. 6,527,282, issued 4 Mar. 2003; U.S. Pat. No. 6,824,147, issued 30 Nov. 2005; and U.S. Pat. No. 6,932,359, issued 23 Aug. 2005. In the meantime, innovation and development has also continued on the snowmobiles themselves. Today, modern snowmobiles have many more comforts and features than earlier models, and because of that, are also much heavier, and, in some cases, have become so heavy that more rugged and robust wheel units are needed.
What is needed therefore is simple and effective method of equipping a snowmobile with a wheel unit.